2018 年 63 巻 3 号 p. 187-191
It is important for precise gravity measurement to calibrate the frequency of a rubidium oscillator as a time frequency standard. We demonstrate simple on-site frequency measurement by using a time frequency calibration tool (FT-001A) with a GPS common view method. We equipped one at the Full Range Seismograph Network of Japan (F-net) Ishigaki (IGK) station, Okinawa, Japan, and measured frequency variation of the internal rubidium oscillator of gPhone gravimeter (#133). As a result, we could measure its frequency with uncertainty of approximately 10-12 (0.01 mHz) on the gravity station 2,000 km apart from AIST Tsukuba where UTC(NMIJ) is maintained.